Address PR feedback, add docs

mrdon-atlassian · bbakerman · commit 5db82e6cdc2f · 2017-11-20T07:50:36.000+11:00
diff --git a/docs/concerns.rst b/docs/concerns.rst
@@ -10,7 +10,7 @@ It does not concern itself about other high level application concerns such as t
 - Data authorisation
 - Data pagination
 - HTTP transfer
-- JSON endoding
+- JSON encoding
 - Code wiring via dependency injection
 
 You need to push these concerns into your business logic layers.
diff --git a/docs/execution.rst b/docs/execution.rst
@@ -137,6 +137,29 @@ behaviour.
         };
         ExecutionStrategy executionStrategy = new AsyncExecutionStrategy(handler);
 
+Returning data and errors
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+It is also possible to return both data and multiple errors in a ``DataFetcher`` implementation by returning
+`graphql.execution.DataFetcherResult` either directly or wrapped in a ``CompletableFuture`` instance for asynchronous
+execution.  This is a useful when your ``DataFetcher`` may need to retrieve data from multiple sources or from another
+GraphQL resource.
+
+In this example, the ``DataFetcher`` retrieves a user from another GraphQL resource and returns its data and errors.
+
+.. code-block:: java
+
+        DataFetcher userDataFetcher = new DataFetcher() {
+            @Override
+            public Object get(DataFetchingEnvironment environment) {
+                Map response = fetchUserFromRemoteGraphQLResource(environment.getArgument("userId"));
+                List<GraphQLError> errors = ((List)response.get("errors")).stream()
+                    .map(MyMapGraphQLError::new)
+                    .collect(Collectors.toList());
+                return new DataFetcherResult(response.get("data"), errors);
+            }
+        };
+
 Serializing results to JSON
 ---------------------------
 
diff --git a/src/main/java/graphql/execution/AbsoluteGraphQLError.java b/src/main/java/graphql/execution/AbsoluteGraphQLError.java
@@ -20,6 +20,8 @@ class AbsoluteGraphQLError implements GraphQLError {
     private final List<SourceLocation> locations;
     private final List<Object> absolutePath;
     private final GraphQLError relativeError;
+    private final String message;
+    private final ErrorType errorType;
 
     AbsoluteGraphQLError(ExecutionStrategyParameters executionStrategyParameters, GraphQLError relativeError) {
         requireNonNull(executionStrategyParameters);
@@ -35,7 +37,7 @@ class AbsoluteGraphQLError implements GraphQLError {
 
         Optional<SourceLocation> baseLocation;
         if (!executionStrategyParameters.field().isEmpty()) {
-            baseLocation = Optional.of(executionStrategyParameters.field().get(0).getSourceLocation());
+            baseLocation = Optional.ofNullable(executionStrategyParameters.field().get(0).getSourceLocation());
         } else {
             baseLocation = Optional.empty();
         }
@@ -49,11 +51,13 @@ class AbsoluteGraphQLError implements GraphQLError {
                                         .orElse(null))
                         .collect(Collectors.toList()))
                 .orElse(null);
+        this.message = relativeError.getMessage();
+        this.errorType = relativeError.getErrorType();
     }
 
     @Override
     public String getMessage() {
-        return relativeError.getMessage();
+        return message;
     }
 
     @Override
@@ -63,7 +67,7 @@ public List<SourceLocation> getLocations() {
 
     @Override
     public ErrorType getErrorType() {
-        return relativeError.getErrorType();
+        return errorType;
     }
 
     @Override
diff --git a/src/main/java/graphql/execution/DataFetcherResult.java b/src/main/java/graphql/execution/DataFetcherResult.java
@@ -27,14 +27,14 @@ public DataFetcherResult(T data, List<GraphQLError> errors) {
     }
 
     /**
-     * @return The data fetched. May be null
+     * @return The data fetched. May be null.
      */
     public T getData() {
         return data;
     }
 
     /**
-     * @return errors encountered when fetching data.  Must not be null.
+     * @return errors encountered when fetching data.  This will be non null but possibly empty.
      */
     public List<GraphQLError> getErrors() {
         return errors;
